Refrigeration system with refrigerant return means



Jan. 6, 1970 w. l. GRANT REFRIGERATION SYSTEM WITH REFRIGERANT RETURN MEANS Filed May 7. 1968 4 R //|O l N E b w n 0 f 4 m M LLV W d 6 M m any: 6 R O o 7 m2 W i W 5 u m E A c 8 w 3 z E w a Z 2 E K INVENTQ: WHITNEY -zn/vr' mam ATTORNEYS United States Patent 3,487,656 REFRIGERATION SYSTEM WITH REFRIGERANT RETURN MEANS Whitney I. Grant, Muskego, Wis., assignor to Vilter Manufacturing Corporation, Milwaukee, Wis., a corporation of Wisconsin Filed May 7, 1968, Ser. No. 729,141

Int. Cl. F25!) 41/00 U.S. Cl. 62--17 4 Claims ABSTRACT OF THE DISCLOSURE BACKGROUND In refrigeration systems of relatively large capacity which include numerous cooling coils or evaporators, it has heretofore been customary to provide a separator communicating with the suction or outlet side of the evaporators for removing the liquid refrigerant from the vapor or gas and for collecting the liquid in an accumulator from which it may be returned to the receiver or high pressure line without entering the compressor. While various systems and methods or returning the liquid refrigerant deposited within the accumulator to the high pressure side of the compressor have heretofore been proposed, such systems have invariably possessed certain disadvantages, the most common of which reside in the complicated, costly and unreliable nature of the systems or components thereof and the requirement for constant attention.

In United States Patent No. 2,724,240, dated Nov. 22, 1955, to Harry Sloan, a refrigeration system is disclosed which obviated many of the disadvantages attendant prior systems of this type and which incorporated automatic means for returning liquid refrigerant derived from the separator directly to the receiver or high pressure side of the system. In such prior patented system, a low differential pressure pump cooperable with valves for periodically equalizing the pressures in the accumulator and receiver of the refrigeration system were incorporated for the purpose of returning excess liquid refrigerant derived from the evaporators by an accumulator to the receiver in an automatic manner. However, even with the system disclosed in Patent No. 2,724,240, certain difficulties have been encountered in refrigeration systems in some plants where the loads on the evaporators at certain periods increase very rapidly thus resulting in a high volume of liquid carryover into the suction trap or accumulator. In such instances, gravity drain of liquid from the suction trap is not rapid enough to lower the level in the trap or accumulator, and as the level therein continues to build up, the danger of the liquid overflowing into the compressor suction line presents itself. Such overflow of liquid into the compressor suction line will ordinarily result in serious and costly damage to the compressors as well as necessitating shutdown of the refrigeration system. Since the prior system was limited by the drainage capacity of liquid by gravity from the suction trap or separator to the accumulator or transfer drum, the abnormal peak periods still presented a problem.

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SUMMARY The present invention contemplates the provision of a high capacity liquid transfer system which obviates the disadvantages attendant prior systems of this general type and which is adapted to effectively accommodate abnormally high loads while eliminating the possibility of refrigerant liquid overflow into the compressor suction line of the system.

Another object of this invention is to provide a simple and reliable system for separating liquid refrigerant from the outlet or suction side of the evaporators of a refrigeration system and for returning the separated liquid refrigerant to the high pressure liquid supply side of the evaporators in a highly effective manner during all periods of operation.

Still another object of the invention is to provide an improved liquid refrigerant separation and return system for large capacity refrigeration plants which embodies means for quickly and effectively removing separated liquid refrigerant from the separation zone and for returning the same to the high pressure side of the system during periods of peak capacity as well as during normal periods of operation.

A further object of the invention is to provide an improved refrigeration system wherein liquid refrigerant is separated from the compressor suction line and is accumulated for return to the receiver, means being provided for rapidly and effectively transferring the separated liquid from the separation zone to the accumulator and for then conveying the accumulated liquid refrigerant back to the receiver.

In accordance with the present invention, a low differential pressure pump is utilized in cooperation with a series of valves for rapidly evacuating a liquid refrigerant separator interposed in the suction line of the refrigeration system and for transferring such separated liquid refrigerant to an accumulator and back to the high pressure side of the system, thus facilitating rapid drainage of the separator to accommodate abnormal as well as normal conditions imposed on the refrigeration system.

These and other objects and advantages of the invention will become apparent from the following detailed description. A clear conception of the various features constituting the present improvement, and of the mode of constructing and operating a typical commercial refrigeration system embodying the invention, may be had by referring to the drawing accompanying and forming a part of this specification wherein like reference characters designate the same or similar parts.

FIGURE 1 is a more or less diagrammatic view of a typical refrigeration installation embodying the improved automatically operable liquid refrigerant separating and return system; and

FIGURE 2 is a typical simple schematic wiring diagram employed for actuating the liquid refrigerant transfer and return pump and its components.

DETAILED DESCRIPTION Referring to the drawing, the refrigeration system diagrammatically illustrated therein comprises, in general, a refrigeration compressor 10 having its low pressure side connected through a suction line 12 with one or more cooling coils or evaporators 14 to receive evaporated or gaseous refrigerant therefrom. The high pressure discharge side of the compressor 10 is, in turn, connected through a delivery pipe or conduit 16 with a condenser 18 for discharging high pressure refrigerant thereto. The lower portion of the condenser 18 communicates with a receiver 20 via conduit 22, and the receiver, in turn, de-

livers liquid refrigerant through line 24 to the inlet of the evaporators 14.

The compressor is adapted to be driven by an electric motor 28 or the like as through a belt drive 30, and the compressor and motor may be mounted as a unit on a suitable stand or platform 32. The compressor 10 as well as the evaporators 14, condenser 18, and receiver may all be of conventional and well-known construction, and the high pressure discharge lines from the receiver to the evaporators may be provided with suitable expansion valves 34 in accordance with customary practice.

Interposed in the suction line 12 is a liquid refrigerant separator or suction trap 38, and the refrigerant drawn from the evaporators 14 is conducted to the trap 38 via conduits 40. Located below the separator or suction trap 38 is an accumulator or transfer drum 42, and the ac cumulator 42 is placed in communication with the lower portion of the separator 38 via conduit 44, 56. Also communicating with conduit 56 is the inlet 36 of a liquid refrigerant pump 46 which discharges through line 48, 52 to the receiver 20, the conduit 52 having a nonreturn check valve 54 therein. The separator 38 may, of course, again be of conventional design adapted to remove liquid refrigerant from the line 40 and thereby prevent migration thereof to the compressor inlet via suction conduit 12, and the accumulator 42 may likewise be of conventional construction with the pump being driven in a customary manner by a motor 58.

The receiver 20 is connected by a conduit 62, 64 with the upper portion of the accumulator 42 past a solenoid valve 66, and the accumulator 42 also communicates with the upper portion of the separator 38 by way of a conduit 68 having a solenoid valve 70 therein. The accumulator 42 is also provided with a conventional float switch 72, and a solenoid valve 74 is interposed in the conduit 44 communicating the separator and accumulator.

The system thus far described is essentially the same as that disclosed in US. Patent No. 2,724,240 hereinabove referred to, and during normal operation of the refrigerating apparatus, the operation is as follows. The excess liquid carried over from the evaporator 14 through line 40 is separated in the separator or suction trap 38, and with solenoid valve 74 open and the gas equalizing solenoid valve 70 likewise open, any liquid which accumulates in the suction trap 38 is permitted to drain by gravity through line 44 and to the accumulator transfer drum 42 via line 56. Thus, the level of liquid refrigerant in the accumulator or transfer drum 42 rises until it reaches the level of the float switch 72. At this point, the float switch actuates the necessary controls to close the solenoid valves 70, 74 and to open the solenoid valve 66 which communicates the accumulator 42 with the high pressure receiver 20. This places high pressure on the accumulator or transfer drum 42, and after a time delay as controlled by a suitable timer 96 (FIGURE 2), the pump 46 commences operation and pumps liquid from the accumulator or drum 42 through lines 56, 36, 48, 52 and past the check valve 54 into the high pressure receiver 20. The operating cycle of the pump is controlled by a suitable timer 76 (FIGURE 2), and when the given time period expires, the operation of the pump is stopped. The equalizing valve 66 thereupon closes, and the low pressure valves 70, 74 open to again permit liquid refrigerant to drain from the separator or suction trap 38 to the accumulator 42.

With the system thus described, the gravity drain of liquid from the separator or suction trap 38 is not fast enough to lower the level in the separator during certain periods when the loads on the evaporators 14 increase rapidly causing a high volume of liquid to be carried over to the separator or suction trap. If this liquid level in the separator 38 continues to build up, there is a danger that the liquid refrigerant will overflow into the compres- .4 sor suction line 12 and then to the compressor inlet, thus resulting in series damage to the compressor. The present improvements are concerned with increasing the capacity of the system which has heretofore been limited by the gravity drain of liquid from the separator 38 to the accumulator 42.

In accordance with the present invention, a liquid level control which may be in the form of a float control switch has been added to the separator or suction trap 38. In addition, a solenoid valve 82 controlled by the liquid level float control switch 80 is placed in conduit 56 to shut off the normal gravity transfer of liquid refrigerant from the separator 38 to the accumulator 42 during the high capacity cycle hereinafter described. Also, the accumulator 42 is placed in communication with the pump discharge line 48, 52 by means of a conduit 84, and flow through the conduit 84 is controlled by a solenoid valve 82 then closes to stop flow from the separator switch 80.

In operation, the float control 80 operates to de-energize the solenoid valve 82 when the level of liquid in the separator 38 reaches a predetermined level. The solenoid valve 82 then closes to stop flow from the separator 38 through conduit 56, and solenoid valve 86 is also opened by the float control switch 80 to permit flow through conduit 84. The float switch 80 also starts operation of the pump 46 which is now in communication with the separator 38 through lines 44, 36 with the solenoid valve 74 open. The liquid refrigerant is accordingly drawn from the separator 38 and is pumped at a high rate from the separator and into the accumulator 42 via conduits 48, 84 past the opensolenoid valve 86. The separator 38 is accordingly rapidly drained and the accumulator 42 is rapidly filled during the periods of peak loads when there is a high volume of liquid carryover from the evaporators 14 into separator 38.

When the level in the accumulator or transfer drum 42 reaches the float control 72, the filling cycle is stopped, solenoid valve 82 is again opened, solenoid valve 86 is again closed, and the pump 46 thereupon becomes elfective to empty the accumulator or transfer drum 42 by conducting liquid refrigerant therefrom through the lines 56, 36, 48 and 52 past check valve 54 to the receiver 20. Since the check valve 54 is exposed to the high pressure in the receiver 20 on one side, the pressure on the pump side of the check valve is always at low pressure during the filling cycle regardless of whether the fill is by gravity or by pump. During the time that pump 46 is pumping liquid from the separator or suction trap 38 into the accumulator or transfer drum 42 through the conduit 84 and past the open valve 86, the check valve 54 remains closed due to the high pressure on the upstream side of the valve. Therefore, when the pump is used to fill accumulator or transfer drum 42, it is still operating at a low pressure difference across the pump.

Referring now to FIGURE 2, the magnetically actuated solenoid valves, float actuated switches, timers, and other electro-mechanical elements of suitable types well known to the refrigeration industry are shown in a schematic form. To facilitate an understanding of the wiring diagram, the magnetic coils 661, 701, 741, 821, and 861 of the solenoid valves 66, 70, 74, 82, and 88 are referred to in this electrical diagram by indicia incorporating the same identifying numerals used in FIGURE 1 to indicate the valve mechanisms in their physical locations.

Automatic motor starter 92 is interposed in electric current supply lines 90 connected to motor 58. The automatic starter includes a coil 92 and plurality of starter contacts 92a, 92b, and 920 in the supply lines. The open ing and closing of the starter contacts is controlled by the energization of coil 92. The timers in the control circuit likewise include energizing coils 76 and 96 which operate timer switching elements 76a and 96a, respectively.

A pair of relays are also included in the electrical circuit of FIGURE 2 to insure proper operation of the circuit. One such relay includes relay coil 94 which controls the opening and closing of relay contains 94a through 94e. The other relay includes coil 95 which operates relay contacts 95a through 95d.

The starter coil 92, which controls the operation of motor 58 and pump 46, may be energized either by accumulator float control switch 72 through timer switch contacts 96a, responsive to the liquid level in the accumulator, or by separator float control switch 80 through the energization of relay coil 94, responsive to the liquid level in separator 38.

Except for the fact that the emptying cycle of the accumulator 42 is timed out by a timer 76, the electrical system as diagrammatically shown in FIGURE 2 is generally the same as that shown and described in United States Patent No. 2,724,240, and reference to such prior patent is hereby made for a more complete description thereof. The entire cycle of operations is automatic and requires no attention on the part of operators or attendants with the above described cycle being repeated upon demand of existing conditions. Since the liquid refrigerant return pump 46 operates only against the static head of refrigerant within the conduit 48, an inexpensive pump requiring a minimum power consumption may be utilized, and due to the fact that the pump operates only under slight differential pressure, its operation is not interrupted by the presence of flash gas within the pump. It is apparent that the present system requires only a single pump adapted to both empty the separator or suction trap 38 under abnormal conditions and to also empty the accumulator or transfer drum when required.

Various modes of carrying out the invention are contemplated as being within the scope of the following claims particularly pointing out and distinctly claiming the subject matter which is regarded as the invention.

I claim:

1. In a refrigerating system having a compressor communicable with the suction line of an evaporator and also communicable with the high pressure refrigerant supply line of the evaporator through a receiver, a separator for removing liquid refrigerant from the suction line, an accumulator communicating with said separator for receiving separated liquid refrigerant therefrom, and conduit means connecting said accumulator with the receiver and having a liquid refrigerant return pump therein operable to transfer liquid refrigerant from said accumulator to the receiver, said pump also being communicable with said separator and selectively operable to transfer separated liquid from said separator to said accumulator.

2. A refrigerating system according to claim 1, wherein the pump inlet is selectively communicable with the accumulator and with the separator and the pump outlet is selectively communicable with the receiver and with the accumulator.

3. A refrigerating system according to claim 2, wherein means responsive to the level of the liquid refrigerant in the accumulator and to the level of the liquid refrigerant in the separator controls pump operation.

4. A refrigerating system according to claim 3, wherein selective communication of the pump inlet and pump outlet is also controlled by the means responsive to the liquid levels in the accumulator and in the separator.

5. A refrigerating system according to claim 4, wherein the means for controlling selective communication of the pump inlet and outlet includes a pair of solenoid valves actuated by float switches.

6. A refrigerant system according to claim 1, wherein means are provided for establishing approximately equal pressures in the receiver and accumulator whenever the pump is operable to transfer liquid from the accumulator to the receiver, and for establishing approximately equal pressures in the accumulator and separator whenever liquid refrigerant is being transferred from the separator to the accumulator.

7. A refrigerating system according to claim 1, wherein means is provided for permitting gravity drain of liquid refrigerant from the separator whenever the pump is inoperable.

8. A refrigerating system according to claim 7, wherein the pump inlet selectively communicates with the sep arator and with the accumulator under the control of a solenoid valve operable in response to the liquid refrigerant levels in the separator and accumulator.

9. A refrigerating system according to claim 8, wherein the pump outlet selectively communicates with the accumulator and with the receiver under the control of a solenoid valve operable in response to the liquid refrigerant levels in the separator and accumulator.

10. A refrigerating system according to claim 9, wherein means responsive to the level of liquid refrigerant in the accumulator controls pump operation independent ly of the means responsive to liquid level in the separator.

References Cited UNITED STATES PATENTS 2,032,286 2/ 1936 Kitzmiller 62-5 12 2,724,240 11/ 1955 Sloan 62174 2,986,898 6/1961 Wood 62174 MEYER PERLIN, Primary Examiner US. Cl. X.R. 

